The following U.S. Pat. Nos. represent the most pertinent prior art relating to the present invention:
3,051,203 PA1 3,092,156 PA1 3,134,409 PA1 3,225,799 PA1 3,965,788
In general, chain saw mills are used to guide the cutting action of a chain saw so that the resulting slabs and lumber pieces have surfaces which are as smooth and parallel as possible. Generally speaking, chain saw mills are used to guide the chain saw bar in a horizontal disposition to make longitudinal cuts through a log, or to maintain the chain saw bar in a vertical disposition to make longitudinal cuts through either a log or a previously cut piece.
One chain saw mill known in the prior art employs a mill frame and a pair of screw jacks extending therefrom to secure the chain saw bar in a horizontal disposition with respect to a previously cut log surface on which the mill frame rests. The mill frame includes a plurality of rollers which allow the frame to translate along the previously cut surface as the chain saw cuts through the wood below.
This form of chain saw mill has been found to be deficient in several important respects. The rollers which purportedly provide easy translation of the mill frame tend to plow into the sawdust which naturally accumulates on the upper surface. When the accumulation becomes too great, the rollers ride up over the sawdust, carrying with them the chain saw bar and causing it to deviate from a planar cutting path through the log. Also, the screw jacks which adjustably support the chain saw bar are subject to rapid corrosion from the wet, acidic sawdust generated by the cutting procedure, as well as from the natural elements which must be accommodated in outdoor cutting procedures. Furthermore, it has been found that when one screw jack is extended a certain amount more than the other, the threaded bores which receive the screw jacks become misaligned therewith, and the screw jacks bind in the bores. It is often quite difficult and time consuming to free the screw jacks and return to normal cutting procedures.
Chain saw mills which support the chain saw bar in a generally vertical disposition while longitudinal cuts are made are quite distinct from the horizontally disposed chain saw mills. These devices generally bolt or clamp to the chain saw bar, and include a carriage which rides on a guide rail or guide track which is secured to the wood being cut. Such devices are extremely laborious and tedious to use, since the guide rail or track must be re-set prior to the initiation of a subsequent cut. The chain saw bar may be spaced in increasing increments from a fixed guide track or rail, one increment for each subsequent cut, but this system results in increasingly less control of the chain saw bar as it is displaced farther from the guiding track.
Most importantly, in the cutting of logs into useful lumber by means of a chain saw, it is necessary to use both forms of chain saw mill; that is, the log is often cut horizontally into slabs, and the slabs are then cut with a vertically disposed chain saw into useful lumber pieces. These two separate cutting procedures necessitate using two different forms of chain saw mill, thus doubling the initial expense, and maintenance expenses for the tools.